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Lambda phage

About: Lambda phage is a research topic. Over the lifetime, 1609 publications have been published within this topic receiving 84675 citations. The topic is also known as: Enterobacteria phage lambda.


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Journal ArticleDOI
TL;DR: It was concluded that the failure of UV to induce lambda(+) in the Rec(-) lysogen was not due to damage to the prophage, but rather to the inability of the irradiated cells to respond by lifting immunity.
Abstract: The behavior of lambda phage in the Rec(-) strain JC-1569 is compared with that in the Rec(+) strain JC-1557. No difference deemed significant was noted in the adsorption rate, latent period, burst size, frequency of lysogenization, and frequency of vegetative phage recombination. The location of the prophage and its mode of insertion in the Rec(-) lysogen of wild-type lambda (lambda(+)) were inferred to be normal from the results of conjugational crosses. Spontaneous and ultraviolet (UV) irradiation induction of lambda(+) were markedly reduced in the Rec(-) lysogen. On the other hand, thermal induction of a mutant lambda (lambdacI857) lysogen of the Rec(-) strain was not reduced and was only slightly affected by UV irradiation. Phage subject to inhibition by lambda immunity failed to multiply in UV-irradiated cells of the Rec(-) lambda(+) lysogen, whereas those not inhibited by this immunity did multiply. It was concluded that the failure of UV to induce lambda(+) in the Rec(-) lysogen was not due to damage to the prophage, but rather to the inability of the irradiated cells to respond by lifting immunity. Preliminary evidence indicates that a single mutation confers recombination deficiency and the inability to lift immunity after UV irradiation. Possible relationships between recombination and the lifting of immunity are enumerated.

189 citations

Journal ArticleDOI
TL;DR: Tn5 lac could be used to assay transcription in any bacterium in which Tn5 can transpose and beta-galactosidase can be measured, and on the regulation of the promoter of the transcription unit, verifying that by transposition Tn 5 lac can fuse lacZ expression to outside promoters.
Abstract: A promoterless trp-lac fusion fragment was inserted near one end of the bacterial transposon Tn5 in the correct orientation to fuse lacZ gene expression to promoters outside Tn5. The resulting transposon, Tn5 lac, retains the kanamycin-resistance gene of Tn5 and transposes in Escherichia coli at 6% the frequency of Tn5 to many different sites in a bacteriophage lambda target. Expression of beta-galactosidase, the product of the lacZ gene, from Tn5 lac insertions in phage lambda depends both on insertion into a transcription unit in the correct orientation and on the regulation of the promoter of the transcription unit, verifying that by transposition Tn5 lac can fuse lacZ expression to outside promoters. An insertion of Tn5 lac in bacteriophage P1 was isolated and used to introduce Tn5 lac into Myxococcus xanthus, a bacterium that undergoes multicellular development. Stable kanamycin-resistant transductants are obtained that contain no P1 DNA sequences but have Tn5 lac inserted at different sites in the Myxococcus chromosome. Individual transductants express different levels of beta-galactosidase. A chromogenic substrate of beta-galactosidase, 5-bromo-4-chloro-3-indolyl beta-D-galactoside, is toxic in Myxococcus when cleaved in large amounts. In principle, Tn5 lac could be used to assay transcription in any bacterium in which Tn5 can transpose and beta-galactosidase can be measured.

188 citations

Journal ArticleDOI
TL;DR: Novel DNA integration strategies are explored that exploit activation or inactivation of genes leading to a selectable phenotype, and asymmetrical regions of homology to control the order of recombination events to open the way to reliable integration of DNA including large synthetic constructs in diverse microorganisms.
Abstract: Most bacteria can only be transformed with circular plasmids, so robust DNA integration methods for these rely upon selection of single-crossover clones followed by counter-selection of double-crossover clones. To overcome the limited availability of heterologous counter-selection markers, here we explore novel DNA integration strategies that do not employ them, and instead exploit (i) activation or inactivation of genes leading to a selectable phenotype, and (ii) asymmetrical regions of homology to control the order of recombination events. We focus here on the industrial biofuel-producing bacterium Clostridium acetobutylicum, which previously lacked robust integration tools, but the approach we have developed is broadly applicable. Large sequences can be delivered in a series of steps, as we demonstrate by inserting the chromosome of phage lambda (minus a region apparently unstable in Escherichia coli in our cloning context) into the chromosome of C. acetobutylicum in three steps. This work should open the way to reliable integration of DNA including large synthetic constructs in diverse microorganisms.

184 citations

Journal ArticleDOI
30 Aug 1990-Nature
TL;DR: The results show that the λ prophage is more tran-scriptionally active than has long been assumed, and suggest that lysogeny may generally have a role in bacterial survival in animal hosts, and perhaps in pathogenesis.
Abstract: ALTHOUGH phage λ represents a well studied biological system, it has certain features that remain obscure. Among these is the function of the roughly one third of the phage genome dispensable for growth in the laboratory, yet retained despite undoubted pressure to economize1. Here we report that these 'accessory' sequences contain two genes which are expressed during lysogeny, and encode host-cell envelope proteins. One of these is lom (ref. 2), the product of which is found in the bacterial outer membrane, and is homologous to virulence proteins of two other enterobacterial genera. The other gene, previously unidentified, we designate bor. Expression of bor significantly increases the survival of the Escherischia coli host cell in animal serum. This property is a well known bacterial virulence determinant3,4—indeed, bor and its adjacent sequences are highly homologous to the iss serum resistance locus of the plasmid ColV2-K94, which confers virulence in animals5,6. These results show that the λ prophage is more tran-scriptionally active than has long been assumed, and suggest that lysogeny may generally have a role in bacterial survival in animal hosts, and perhaps in pathogenesis.

181 citations

Journal ArticleDOI
06 Mar 1992-Cell
TL;DR: The 21 kd NusG protein is essential for E. coli viability and inactivated the phage HK022 Nun termination factor and the factor-independent lambda tl terminator was fully active in Nus G-depleted cells and could be suppressed by phage lambda N function.

176 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20226
20219
20209
20195
20188
20177